The present invention relates to automated transmission systems, and in particular automated manual, semi-automatic and fully automatic transmission systems that use a multiple-ratio transmission that has synchronizers on the gear steps.
In automated transmission systems that use multiple-ratio transmissions in which the engagement of the gears is regulated by synchronizers, as are disclosed in, for example, GB2308413; GB2354296; GB2354295; GB2358443; GB0105186.1; GB0029453.8; GB0026423.4; GB0025848.3; GB0025847.5; GB0029454.6; GB0025000.1; GB0024999.5; GB0026178.4; GB0027640.2; GB0028310.1; GB0031624.0; GB103312.5, whereby reference will be made exclusively to these disclosures and their content is incorporated in the disclosure content of the present application; the synchronizer is used to brake or accelerate the drive shaft of the transmission until the speed for the intended target gear is reached. Therefore, the synchronizer, as far as its action is concerned, is a friction device that is capable of transmitting a limited torque. The required torque is determined by the inertia of the drive shaft and by the time that is available for the complete synchronization. The synchronization time is a function of the magnitude of the required speed change. Traditionally, the synchronizers that are associated with the various gears have different performance capabilities that take into account the intended braking torque, the frequency of use and the average speed change.
It is desirable to regulate the torsional force that acts on the synchronizers in order to ensure that the torque acting on them, and consequently the synchronizer wear, do not become too great. Previously, this was achieved by regulating the force that acts on the synchronizer via an actuating mechanism, the actuating force corresponding to an optimal torsional force for the synchronizer that is empirically predetermined on the basis of steady load tests by the transmission manufacturer.
The torsional forces that act on the synchronizers change along with the speed change and also with the temperature changes of the transmission oil. Adjustments may be implemented via the actuation force that acts on the synchronizers in order to incorporate such changes. However, such changes can only be approximations and, while the regulation of the actuation force on the synchronizers is improved, it cannot be guaranteed that the torsional forces corresponding to the predetermined maximum synchronization forces prescribed by the manufacturer are not exceeded. Moreover, in order to implement such adjustments, additional sensors are required to record changes in the temperature and speed differentials.
Furthermore, other factors, such as the wear of the components mounted on the transmission drive shaft, and especially a driven clutch plate, and changes in the friction coefficient of the synchronizer that are not foreseeable and are not precisely applicable for the adjustments also have effects on the torque that is applied by the synchronizer and on the rate of change of the drive shaft speed.